Grade of similarity

Effect of Molecular Weight of Polyvinyl Alcohol. The table shows the rates observed with a standard concentration (0.36% w/v) of grades of similar acetyl content (12-13 mole %) for the polymerisation of 2% vinyl acetate solutions. The 4% solution viscosities are either the means of the range specified for the grade or, for the Gohsenol series, actual batch values. 

Common grades of laminates tend to be thin materials ranging from 0.5—1.5 mm in thickness, therefore for most appHcations they must be supported. In the manufacture of furniture, cabinetry, and countertops the laminates are bonded to particle board or plywood. Since the laminates consist largely of ceUulosic paper, their dimensional stabiHty is similar to wood, particularly to particle board. 

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

Iron—Aluminum and Iron—Aluminum—Silicon Alloys. The influence of aluminum on the physical and magnetic properties of iron is similar to that of silicon, ie, stabilization of the bcc phase, increased resistivity, decreased ductility, and decreased saturation magnetization, magnetocrystalline anisotropy, and magnetostriction. Whereas Si—Ee alloys are well estabHshed for electrical appHcations, the aluminum—iron alloys have not been studied commercially. However, small (up to ca 0.3%) amounts of A1 have been added to the nonoriented grades of siHcon steel, because the decrease in ductiHty is less with A1 than with Si. 

Sodium carboxymethyl cellulose [9004-32-4] (CMC) and hydroxyethyl cellulose [9004-62-0] (HEC) are the ceUulosics most widely used in drilling fluids (43). CMC is manufactured by carboxymethylation of cellulose which changes the water-insoluble cellulose into the water-soluble CMC (44). Hydroxyethyl cellulose and carboxymethyl hydroxyethyl cellulose (CMHEC) are made by a similar process. The viscosity grade of the material is determined by the degree of substitution and the molecular weight of the finished product. 

Commercial grades of socbum aluminate contain both waters of hycbation and excess socbum hycboxide. In solution, a high pH retards the reversion of socbum aluminate to insoluble aluminum hycboxide. The chemical identity of the soluble species in socbum aluminate solutions has been the focus of much work (1). Solutions of sodium aluminate appear to be totaby ionic. The aluminate ion is monovalent and the predominant species present is deterrnined by the Na20 concentration. The tetrahydroxyaluminate ion [14485-39-3], Al(OH) 4, exists in lower concentrations of caustic dehydration of Al(OH) 4, to the aluminate ion [20653-98-9], A10 2) is postulated at concentrations of Na20 above 25%. The formation of polymeric aluminate ions similar to the positively charged polymeric ions formed by hydrolysis of aluminum at low pH does not seem to occur. Al(OH) 4 has been identified as the predominant ion in dilute aluminate solutions (2). 

DOT 17E phenolic-lined steel pails and dmms, respectively. Plain steel is not suitable for isopropyl alcohol containing water because msting can result. Instead, baked phenolic-lined steel tanks are used. Aluminum is also unsuitable. It is attacked by isopropyl alcohol, especially the anhydrous grade, resulting ia the formation of aluminum isopropoxide. Containers must comply with DOT specifications. Tanks, piping, and equipment can be made of similar material. 

SheUac has had a commercial history similar to that of the traditional resins. It has been replaced by synthetic resins in many appHcations. In the 1950s, about 19,000 t of various grades of processed sheUac were available in the United States. The volume was about 5,500 t in 1995. The largest importer of sheUac is William Zinsser Company, Inc. The superior grades of sheUac are sold for about 6.60— 9.90/kg, depending on quaHty. 

Ferrosihcon production is a nearly slag-free process. Most of the impurities introduced into the furnace via the raw materials and any other sources are transferred to the product. In order to produce high purity grades of ferrosihcon, the tapped ahoy is refined by treating with gas mixtures and slag additions. The principle of ferrosihcon refining is quite similar to that of sihcon. Details on the thermochemistry of ferrosihcon refining and practical examples are available (24). 

In ancient India, a steel called wootz was made by placing very pure kon ore and wood or other carbonaceous material in a tightly sealed pot or cmcible heated to high temperature for a considerable time. Some of the carbon in the cmcible reduced the kon ore to metallic kon, which absorbed any excess carbon. The resulting kon—carbon alloy was an excellent grade of steel. In a similar way, pieces of low carbon wrought kon were placed in a pot along with a form of carbon and melted to make a fine steel. A variation of this method, in which bars that had been carburized by the cementation process were melted in a sealed pot to make steel of the best quaUty, became known as the cmcible process. 

Typical specifications for several common types or grades of acid are shown in Table 13. Similar limits are generally used for other sulfuric acid concentrations, with the exception of turbidity values for high strength acids (and oleum) and SO2 and nitrate values in oleums. Because kon sulfate is relatively insoluble in concentrated acids, the turbidities of 98—99% H2SO4 and oleum may be higher than shown, even at acceptable total kon concentrations. 

Agricultural grades of ammonium thiosulfate are prepared by similar processes and contain some excess sulfur. The sulfur can be removed by washiug with carbon disulfide. A typical sulfur-free product contaius 87% (NH 2S203 3.4% (NH 2SC)3, and 9.6% (NH 2SC)4 (67). 

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